package com.summer.sqlSession;

import com.summer.config.BoundSql;
import com.summer.pojo.Configuration;
import com.summer.pojo.MappedStatement;
import com.summer.utils.GenericTokenParser;
import com.summer.utils.ParameterMapping;
import com.summer.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.util.ArrayList;
import java.util.List;

public class SimpleExecutor implements Executor {
    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        //注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();

        //1、获取sql语句 select * from user where id = #{id} and username= #{username}
        String sql = mappedStatement.getSql();
        //2、转换sql语句 : select * from user where id = ? and username= ? 转换的过程中还需要对#{}里面的值进行解析存储
        BoundSql boundSql = getBoundSql(sql);
        //3、获取预处理对象 preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
        //4、设置参数
        //获取参数的全路径
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramterTypeCLass = getClassType(paramterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            //反射
            try {
                Field declaredField = paramterTypeCLass.getDeclaredField(content);
                //设置暴力访问
                declaredField.setAccessible(true);
                Object o = declaredField.get(params[0]);  //user
                //设置参数 当前下标是从0开始  而设置参数是从1开始的 所以是i+1
                preparedStatement.setObject(i+1,o);

            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        //5、执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);
        Object o = resultTypeClass.newInstance();

        ArrayList<Object> objects = new ArrayList<>();
        //6、封装返回结果集 对resultSet进行遍历
        while (resultSet.next()){
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            //下标从1开始 是因为获取字段名是从1开始
            for (int i = 1; i < metaData.getColumnCount(); i++) {
                //字段名
                String columnName = metaData.getColumnName(i);
                //字段值
                Object value = resultSet.getObject(columnName);
                //使用反射或者内省 根据数据库表和实体的对应关系 完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o,value);
            }
        }

        objects.add(o);
        return (List<E>) objects;
    }

    private Class<?> getClassType(String paramterType) throws ClassNotFoundException {
        if(paramterType != null){
            Class<?> aClass = Class.forName(paramterType);
            return aClass;
        }
        return null;
    }

    /**
     * 完成对#{}的解析工作：1、将#{}使用？进行代替 2、解析出#{}里面的值进行存储
     *
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        ParameterMappingTokenHandler mappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "#}", mappingTokenHandler);
        //完成对占位符的解析处理 即解析处理的sql
        String parseSql = genericTokenParser.parse(sql);
        //#{}解析出来的参数名称
        List<ParameterMapping> parameterMappings = mappingTokenHandler.getParameterMappings();
        BoundSql boundSql = new BoundSql(parseSql, parameterMappings);
        return boundSql;
    }

    @Override
    public Integer update(Configuration configuration, MappedStatement mappedStatement, Object... params) {
        return null;
    }

    @Override
    public Integer delete(Configuration configuration, MappedStatement mappedStatement, Object... params) {
        return null;
    }
}
